Rheostat control



July 22,194L J. H. ERQWNFEEZLD RHEOSTAT CONTROL Filed. Nov. 17, 1939 2 Sheets--S11eei; l

INVENTOR i JOHN H. BROWNFIELD ATTORN y 1941 Y J: H. BROWQFIELQ" 2,249,738

RHEOSTAT CONTROL Filed Nov. 17, 1939 2 Sheets-ShQQt 2 INVENTOR JOHN BROWNFIELD BY Z i i l v ATTOR Y Patented July 22, 1941 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 3 Claims.

This invention relates to a rheostat control or current regulator for electrical devices such as motors or the like, wherein it is desirable that the current be fed thereto at a predeterminable rate to thus prevent injury to machinery caused by an excess of current before the machinery has picked up its load.

A further object of this invention is to provide a rheostat control or switch for the starting and control of A. C. or D. C. motors which may be operated instantly yet which will interpose a resistance between the source of current and the motor and will cut out the resistance at a rate predeterminable according to the particular setting of a valve.

A further object of this invention is to provide a control switch for motors which, although it includes the passage of a quantity of mercury from one container to another container through a valve to progressively cut out resistance according to the rate of flow of the mercury or other electroconductive fluid, yet can be used for marine motor starting applications due to the presence of an additional solenoid operated valve in the interconnecting line which will maintain the mercury level substantially constant in the rheostat mercury container in spite of the roll and pitch of a ship on which it may be located.

With the foregoing and other objects in view, the invention consists in the construction, combination and arrangement of parts hereinafter described and illustrated in the drawings, in which,

Fig. 1 is a schematic view of one form of the invention; and

Fig. 2 is a schematic View of a slightly modified form of the invention.

There is shown at It) a reservoir properly insulated on the inside and connected by a tubing H to a contact cylinder l2. This contact cylinder is fixedly mounted on a supporting wall or surface and is provided'with a non-amalgamating copper bus l3 extending vertically on the inside thereof, which has pivoted thereto near its top a copper fioat l4 adapted to bridge the space therebewteen to a copper contact l5 connected by a line It to the motor I! which is to be operated.

The contact cylinder l2 also contains a plurality of vertically spaced contacts I8, each connected through its line l9 and through rheostat resistor elements or auto transformer to the line iii to lead to the motor. The tops of the reservoir 10 and contact cylinder l2 are interconnected by a tubing 2!. The reservoir 10 is provided with a quantity of electroconductive fluid such as mercury 22 which flows through the tubing H to the contact cylinder 12. The reservoir i0 is mounted for vertical movement on a guide 23 and may be raised by means of a handle 24 until the lug 25 contacts and is held by an overload release 26 which is placed in a line 21 between the motor I! and double pole line switch 28, copper bus l3 also beingconnected by line 30 to the double pole switch 28.

The current is supplied through the double pole switch by means of the'lines 3| leading to the line terminals 32 connected to any suitable source of electrical energy. The tubing Zl'and upper portions of the reservoir 10 and contact cylinder l2 may be filled with an inert gas or provided with a vacuum so as to prevent any oxidizing of the electroconductive fluid. The reservoir I0 is provided with a switch operating prong 33 cooperating with the bifurcated fingers 34 and 35 of the double pole switch 28 so as to keep this switch in the off positionwhen the reservoir I0 is at the bottom of the guide 23 and to move it to the on position when the reservoir [0 is raised vertically to the uppermost position.

As the reservoir I0 is thus raised vertically, the electroconductive fiuidin the reservoir l0 commences to flow through the tubing II to the contact cylinder I2. This rate of flow may be controlled by means of a gate valve 36, which may be set so as to cause the contact cylinder I2 to be filled up at any desired rate, according to the characteristics of the motor I! which'is to be operated. When the motor is to be cut off the reservoir 13 is merely lowered by means of its handle 24,'causing the prong 33 to operate finger 34 and move the double pole switch 28 to the off position. Inasmuch as it may be desirable to immediately re-start the motor without waiting for'the electroconductive fluid to flow back through the control valve 36 at the same rate as in starting, a by-pass check valve 31 is provided, permitting the fluid to flow back at a rapid rate.

If used on shipboard for marine motors it is desirable to prevent the pitch and roll of the ship from causing the electroconductive fluid level to oscillate. To take care of this a solenoid valve 38 is provided in tubing ll adapted to remain normally open, except when the current is flowing through an auxiliary contact 42 to the motor l1, being connected thereto by means of the lines 39 and 40. When so used for marine motors the tubing 2| may be filled with any liquid having good dielectric properties in place of the vacuum or the inert gas, and a small expansion chamber 4| of the flexible bellow type is provided to take care of the expansion of the mercury and the dielectric liquid.

In operation, the reservoir I is raised along the guide 23 to the topmost position to start the motor, and is lowered to the lowermost position to stop the motor, the valve 36 having first been set to allow the fluid to flow from the reservoir ID to the contact cylinder I2 at the desired rate according to the characteristics of the motor. The fluid flowing through the tube I I into the contact cylinder l2 bridges the copper bus l3 to the copper contacts l8 and flows into the contact cylinder l2, progressively cutting out the resistance in the rheostat 20 until it finally reaches the topmost contact I and causes the copper float M to bridge thereacross, thereby cutting out all of the resistance and allowing the full current to flow to the motor 11. Simultaneously, in a marine installation, the solenoid valve 38 will be closed and prevent any oscillation of the fluid from the reservoir ID to the contact cylinder [2, and vice versa. The reservoir II] will be so placed relative to the cylinder [2 that the lowermost contact l8 will always be covered by the electroconductive fluid, and due to the small voltage difierences as the resistances in the rheostat 20 are progressively cut out, there will be little or no arcing present.

In the form of the invention shown in Fig. 2, the reference numerals are primed where they correspond in function and are similar in construction to that of the form shown in Fig. 1. In this form the reservoir I0 is mounted on a wheel or spider 50 which also carries a contact cylinder l2. The wheel or spider 50 is mounted for rotation about a pivot 5| and has a stop 52 limiting its rotation in the off direction, while a spring 53 tends to rotate it to such off position. To operate the motor ll the spider 50 is rotated about 20 degrees until it reaches the overload release 26' holding it in such position with the mercury 22 filling the cylinder l2 and causing float [4' to bridge from bus l3 to contact l5. and construction of this form is substantially identical with that of the other form.

Other modifications and changes in the proportions and arrangements of the parts may be made by those skilled in the art without departing from the nature of the invention, within the scope of what is hereinafter claimed.

The invention described herein may be manufactured and/or used by or for the Government of the United States of America for governmental purposes without the payment of any royalty thereon or therefor.

Having thus set forth and disclosed the nature of the invention, what is clalmed is:

1. In a current regulator for electrical devices comprising a pair of interconnected receptacles adapted to contain an electroconductive liquid, a vertically extending contact member in one of said receptacles adapted to be connected to one of a pair of lines leading to a source of power,

Otherwise the operation a plurality of vertically spaced apart contact members in said receptacle spaced from said vertical contact member, a tube means interconnecting said receptacles and means for mounting one of said receptacles for vertical displacement relative to the other of said receptacles whereby the level of the electroconductive liquid may be changed to progressively bridge said vertically spaced contact members to said vertically extending contact member, said mounting means for said one receptacle comprising a vertical guide, a switch in said power lines limiting the movement of said receptacle in one direction and means limiting the movement of said receptacle in the other direction.

2. In a current regulator for electrical devices comprising a pair of interconnected receptacles adapted to contain an electroconductive liquid, a vertically extending contact member in one of said receptacles adapted to be connected to one of a pair of lines leading to a source of power, a plurality of vertically spaced apart contact members in said receptacle spaced from said vertical contact member, a tube means interconnecting said receptacles and means for mounting one of said receptacles for vertical displacement relative to the other of said receptacles whereby the level of the electroconductive liquid may be changed to progressively bridge said vertically spaced contact members to said vertically extending contact member, said mounting means for said one receptacle comprising a wheel on which said receptacle is mounted, a switch in said power lines limiting the rotation of said wheel and receptacle in one direction, and means limiting the rotation of said wheel and receptacle in the other direction.

3. In a current regulator for electrical devices comprising a pair of interconnected receptacles adapted to contain an electroconductive liquid, a vertically extending contact member in one of said receptacles adapted to be connected to one of a pair of lines leading to a source of power, a plurality of vertically spaced apart contact members in said receptacles spaced from said vertical contact member, a tube means interconnecting said receptacles and means for mounting one of said receptacles for vertical displacement relative to the other of said receptacles whereby the level of the electroconductive liquid may be changed to progressively bridge said vertically spaced contact members to said vertically extending contact member, said mounting means for said one receptacle comprising a wheel on which said receptacle is mounted, a switch in said power lines limiting the rotation of said wheel and receptacle in one direction, means limiting the rotation of said wheel and receptacle in the other direction, said limiting means normally holding said wheel against release, and yieldable means urging said wheel to rotate toward said switch when released.

JOHN H. BROWNFEEILD. 

